This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-328800, filed Nov. 18, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a method of forming a film on a substrate and an apparatus thereof.
In a photolithography process in the semiconductor device fabrication processes, for example, resist coating treatment in which a resist solution is applied to the surface of a wafer to form a resist film, exposure processing in which the wafer is exposed in a pattern, developing treatment in which development is performed for the exposed wafer, and the like are performed to form a predetermined circuit pattern on the wafer.
At present, in the above-described resist coating treatment, a spin coating method is in the mainstream as a method of applying the resist solution. According to the spin coating method, the resist solution is discharged to the center of the wafer and the wafer is rotated. This allows the resist solution applied on the wafer to spread by centrifugal force, whereby a uniform resist film can be formed over the entire face of the wafer.
However, in the spin coating method, since the wafer is rotated at high speed, a large amount of resist solution scatters from the peripheral portion of the wafer, resulting in a big waste of resist solution. Further, the apparatus is contaminated by the scatter of the resist solution, bringing about harmful effects such as a need for cleaning frequently.
Hence, instead of the spin coating method in which the wafer is rotated, a method, in which a nozzle for discharging the resist solution and the wafer move relative to each other to apply the resist solution, for example, evenly on the wafer in lattice form, is conceivable.
However, in the case in which the resist solution is applied in the manner of the so-called single stroke, it is feared that the resist solution applied at the peripheral portion of the wafer protrudes by surface tension, with the result that a resist film is not uniformly formed. When exposure is performed with the resist film protruding at the peripheral portion, the peripheral portion becomes a defective portion which can not be used as products, whereby yields correspondingly decrease.
The present invention is made in consideration of the above points and its object is to provide a film forming method, which basically employs a method of forming a film on a substrate by discharging a coating solution while a coating solution discharge member such as the aforesaid nozzle and a substrate such as a wafer move relative to each other, in which a uniform resist film is formed also at an outer peripheral portion of the substrate, and a film forming apparatus having the above functions.
In the consideration of the above object, the method of the present invention is a method of forming a film of a coating solution on a substrate through the use of a coating solution discharge member, comprising the steps of: moving the coating solution discharge member relative to the substrate while the coating solution is being discharged from the coating solution discharge member to the surface of the substrate; and changing a discharge direction of the coating solution to an outer peripheral portion of the substrate to make the amount of application to the outer peripheral portion smaller than that to other portions.
Further, the apparatus of the present invention is a film forming apparatus for a substrate including a coating solution discharge member for discharging a coating solution to the substrate, comprising: coating solution suction means for sucking the coating solution discharged from the coating solution discharge member to an outer peripheral portion of the substrate before the coating solution reaches the substrate, the coating solution discharge member being movable relative to the substrate while discharging the coating solution to the surface of the substrate.
The apparatus of the present invention may not include the suction means, but the coating solution discharge member may be arranged such that a discharge direction of the coating solution to the outer peripheral portion of the substrate is changeable.
The apparatus of the present invention may have gas supply means for blowing a predetermined gas to the coating solution discharged from the coating solution discharge member to the outer peripheral portion of the substrate before the coating solution reaches the substrate in place of the suction means.
According to the present invention, it is possible to change the discharge direction of the coating solution to the outer peripheral portion of the substrate, thereby reducing the amount of application to the outer peripheral portion of the substrate, so that it is possible to restrain protuberance of the coating solution at the outer peripheral portion of the substrate caused by surface tension. Consequently, a uniform coating film is formed also at the outer peripheral portion on the substrate, and thus a region on the substrate which can be used as products is increased in area to improve yields.
The discharge direction of the coating solution is changed only when the coating solution discharge member moves from the inside to the outside of the substrate to thereby cross the outer peripheral portion of the substrate or when it reversely moves from the outside to the inside of the substrate to thereby cross the outer peripheral portion of the substrate, whereby the discharge is performed, as a result, only when the coating solution discharge member moves in one direction, so that the amount of application to the outer peripheral portion of the substrate is reduced to half. Accordingly, protuberance at the outer peripheral portion is restrained to thereby improve yields. Moreover, the amount of application can be reduced correspondingly, resulting in reduced cost.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.